Method of manufacturing sandwich elements

ABSTRACT

1. A METHOD OF MANUFACTURING SANDWICH ELEMENTS, COMPRISING THE STEPS OF SPREADING OUT A FIRST LAYER OF A MIXTURE OF SOLID PARTICLES AND LIQUID RESINOUS BINDER ON A BASE, APPLYING A SUPPORT MEMBER OF FLEXIBLE SHEET MATERIAL ON THE SURFACE OF SAID FIRST LAYER, SPREADING OUT A SECOND LAYER OF A MIXTURE OF SOLID PARTICLES AND LIQUID RESINOUS BINDER ON SAID FIRST LAYER AND SAID SUPPORT MEMBER, THE QUANTITY OF SOLID PARTICLES IN SAID MIXTURE FORMING SAID SECOND LAYER BEING SUCH THAT UPON SUBSEQUENTLY ALLOWING THE SOLID PARTICLES TO SETTLE AND TO FORM A SETTLE LAYER OF PARTICLES WITH BINDER THEREBETWEEN, AN OUTER LAYER OF BINDER IN EXCESS OF THAT WHICH SETTLES BETWEEN THE PARTICLES IS FORMED ATOP SAID SETTLED LAYER, INSERTING ONE SIDE PORTION OF A CORE BOARD ELEMENT OF OPEN-CELLED STRUCTURE INTO AND THROUGH SAID OUTER LAYER AND INTO ENGAGEMENT WITH SAID SUPPORT MEMBER, AND SAID SUPPORT MEMBER SEEPING SAID CORE BOARD ELENENT OUT OF CONTACT WITH SAID BASE, SO THAT SOME BINDER OF SAID OUTER LAYER ENTERS AND IS PICKED UP BY THE CELLS OF SAID CORE BOARD ELEMENT, AND FINALLY ALLOWING SAID BINDER TO HARDEN.

Oct. 22, 1974 v K. L.B.JOHANSSON ETAL 3,843,486

METHOD OF MANUFACTURING SANDWIC}! ELEMENTS Filed April 21. 1971 Fig.1

United States Patent US. Cl. 156276 2 Claims ABSTRACT OF THE DISCLOSURE A method of manufacturing sandwich elements by spreading a mixture of solid particles and liquid resinous binder on a base as a layer, applying a flexible sheet on the surface of this first layer, then spreading out a second layer of particles and binder on the sheet and allowing the solid particles to settle and to form a settled layer of particles and an outer layer of binder in excess of that which settles between the particles, inserting a core board element of open celled structure into and through the outer layer and into engagement with said support member, so that some binder is picked up by the cells of said core board element, and finally allowing the binder to harden. The face of a panel so formed is not marked by the core material.

The present invention relates to an improved method of manufacturing sandwich elements which can be used as wall or floor panels in buildings.

There is known to the art a method for manufacturing sandwich elements according to which a mixture of solid particles and liquid resinous binder is spread on a base, the quantity of said binder exceeding the volume of the spaces between the solid particles, whereafter the solid particles are allowed to settle so that a settled layer of particles and an outer layer of excess binder is formed. This outer layer is then broken by inserting therein one side of a distance material, such as a core board element of open celled structure, and then the binder is allowed to harden. The other opposite side of the distance material may also be inserted in an outer layer of excess binder of a similar external unit consisting of a settled layer of solid particles and an outer layer of excess binder.

It has been found when manufacturing such sandwich elements that the distance material is liable to penetrate to different depths in the external unit or units, thereby causing the pattern of the distance material to be visible in patches on the external unit or units of the sandwich elements. Moreover, the degree of adhesion between the external unit or units and the distance material will vary with the depth to which the distance material penetrates into the external unit or units. Another disadvantage is that the thickness of a number of sandwich elements as well as the thickness of one sandwich element varies, owing to the fact that the distance material penetrates into the external unit or units to different depths.

The main object of the present invention is therefore to eliminate these disadvantages. With the improved method of the present invention, a strip-like support member of flexible sheet material intended to regulate the depth to which the distance material penetrates into the external unit or units of the sandwich element is applied in said external unit or units when each of said units is spread out on a base, at a predetermined level from the base. The method comprises the steps of spreading out a first layer of a mixture of solid particles and liquid resinous binder on a base, applying a strip-like support member on the surface of said first layer, spreading out a second layer of a mixture of solid particles and liquid resinous binder on said first layer and said support member, the quantity of "Ice the binder in at least said mixture forming said second layer exceeding the volume of spaces between the solid particles in said mixture forming said second layer, subsequently allowing the solid particles to settle and to form a settled layer of particles with binder therebetween, forming from the excess binder an outer layer, inserting into said outer layer and into engagement with said support member one side of a distance material of cellular structure to at least partially absorb and/or pick up said excess binder, and finally allowing said binder to harden.

The method of the present invention may be used to produce both flat and curved sandwich structures, in which one or both sides of the core element, i.e., the distance material is or are united with a spread-out layer of binder and solid particles in accordance with the improved meth- 0d.

The invention will now be described in detail with reference to the accompanying drawing, in which FIG. 1 illustrates by way of example a system for spreading out an external unit of a sandwich element, and FIG. 2 illustrates a cross section of a part of a sandwich element manufactured in accordance with the invention.

A first layer 3 of the mixture of liquid resinous binder and solid particles is spread out by means of a doctor device 2 on a fiat base 1, which is arranged to move in the direction indicated by the arrow A, the mixture being supplied from a first supply 4. At the same time as the first layer is spread out on the base by the doctor device 2, a strip-like support member shown as a sheet of flexible material 6 is fed from a supply reel 5 between the supply 4 and the doctor device 2 in a manner whereby the support member 6 lies substantially in the surface of the first layer 3. Located behind the doctor device 2, when seen in the direction of movement of the base 1, is a further doctor device 7 which is arranged to spread out a second layer 8 of a mixture of liquid resinous binder and solid particles, this latter mixture being supplied from a second supply 9. The quantity of binder in the latter mixture exceeds the volume of the spaces between the solid particles. The solid particles in the second layer 8 spread out by the doctor device 7 are allowed to settle so that an outer layer 10 consisting substantially of the excess binder and a settled layer 11 of particles with binder therebetween is formed progressively as the layer 8 is distributed.

The combined layer or external unit 12 of binder and solid particles and the support member 6 enclosed therein is then united with a core or distance material 13, by means of which the outer layer 10 of excess binder is broken. The distance material 13 is inserted into the outer layer 10 and into engagement with the support member 6, which is located at a predetermined distance from the outer surface 14 of the sandwich element. The distance material 13 absorbs and/or picks up the outer layer 10 of excess binder. The quantity of excess binder forming the outer layer 10 is adjusted so that the excess provides for sufficient contact with or adhesion to the located distance material 13, thereby providing an effective connection between the distance material and the external unit 12 of the sandwich element. The excess binder also serves to facilitate the distribution of the mixture of binder and solid particles by means of the doctor device 7. It is therefore to advantage to include an excess of binder in the mixture distributed from the supply 4. This latter excess may be collected at the outer layer 10, owing to the fact that the particles in the second layer 8 settle down to the first layer 3, the particles of which also settle, although the latter excess of binder may also be absorbed entirely or partially by the inserted support member 6, which may consist of an absorbent material. The quantity of excess binder in the two mixtures need not necessarily be the same.

As illustrated in FIG. 2, the other opposite side of the distance material may also be united with a combined layer or external unit 12 of binder and settled particles produced on a base in a manner similar to that described in the aforegoing.

The support member intended to fix the position of the distance material may consist of a materiai which cmpletely or partially absorbs a possible excess of binder present in the first layer 3. The support member may also consist of an absorptive or a non-absorptive material which is permeable to the binder and the solid particles thereby permitting a possible excess of binder present in the first layer 3 to collect at the surface, owing to the fact that solid particles in the second layer are able to pass through the permeable support member when settling. Paper, net structures of metal or plastics, gauze ribbon and fabric of glass fibre are examples of suitable material for the support member.

The liquid resinous binder may, for example, be an isophthalic, phthalic, bisphenolic or other polyester containing a curing agent in the form of, for instance, hexamethylenetetramine. Further examples of a binder which may be used with the present invention are polyvinyl chlorides, polyvinyl acetates, polymers of polyethers, poly urethanes, polyethylenes, combinations of phenol formaldehydes, and synthetic resins of epoxy type.

The solid particles present in the mixtures may comprise sand, e.g. having an average grain size of 0.15 mm. The solid particles may also comprise, for example, stone powder, stone crush, granular slag or metal powder or suitable mixtures of these materials (including sand).

The distance material is intended to break or penetrate the outer layer of excess binder collected at the surface and may therefore consists of a material which entirely or partially absorbs the excess binder, or may be in the form of a material which picks up the excess binder in spaces in the distance material without absorping the same as shown in FIG. 2. Examples of suitable distance material include corrugated board and so-called honeycomb board and similar material having a cellular structure. As an absorbent distance material it is possible to use a mixture of sand with a deficiency of polyester.

The base onto which the first layer is spread out may be made, for example, of glass or stainless metal sheet. The base is treated with a suitable release agent for facilitate removal of the base from the finished sandwich structure. The binder may also be spread out on a base which is intended to be included in the finished sandwich structure. For example, a fireproof sandwich element can be produced by spreading out the binder or the particles on gypsum board.

The term second layer used in the aforegoing and in the following claims refers to a layer which may be either continuous or discontinuous. Thus, the second layer may also be applied in zones.

What we claim is:

1. A method of manufacturing sandwich elements, comprising the steps of spreading out a first layer of a mixture of solid particles and liquid resinous binder on a base, applying a support member of flexible sheet material on the surface of said first layer, spreading out a second layer of a mixture of solid particles and liquid resinous binder on said first layer and said support member, the quantity of solid particles in said mixture forming said second layer being such that upon subsequently allowing the solid particles to settle and to form a settled layer of particles with binder therebetween, an outer layer of binder in excess of that which settles between the particles is formed atop said settled layer, inserting one side portion of a core board element of open-celled structure into and through said outer layer and into engagement with said support member, and said support member keeping said core board element out of contact with said base, so that some binder of said outer layer enters and is picked up by the cells of said core board element, and finally allowing said binder to harden.

2. A method according to claim 1, wherein an opposite side portion of said core board element is also inserted into another composite layer formed according to claim 1, after which the binder is allowed to harden on both sides of the core board element simultaneously.

References Cited UNITED STATES PATENTS 1,504,805 8/1924 Borsodi 156-276 2,748,019 5/1956 Schramn 156276 2,831,794 4/ 8 Elemendorf 156-276 DAVID KLEIN, Primary Examiner J. L. GOODROW, Assistant Examiner U.S. Cl. X.R. 156280 

1. A METHOD OF MANUFACTURING SANDWICH ELEMENTS, COMPRISING THE STEPS OF SPREADING OUT A FIRST LAYER OF A MIXTURE OF SOLID PARTICLES AND LIQUID RESINOUS BINDER ON A BASE, APPLYING A SUPPORT MEMBER OF FLEXIBLE SHEET MATERIAL ON THE SURFACE OF SAID FIRST LAYER, SPREADING OUT A SECOND LAYER OF A MIXTURE OF SOLID PARTICLES AND LIQUID RESINOUS BINDER ON SAID FIRST LAYER AND SAID SUPPORT MEMBER, THE QUANTITY OF SOLID PARTICLES IN SAID MIXTURE FORMING SAID SECOND LAYER BEING SUCH THAT UPON SUBSEQUENTLY ALLOWING THE SOLID PARTICLES TO SETTLE AND TO FORM A SETTLE LAYER OF PARTICLES WITH BINDER THEREBETWEEN, AN OUTER LAYER OF BINDER IN EXCESS OF THAT WHICH SETTLES BETWEEN THE PARTICLES IS FORMED ATOP SAID SETTLED LAYER, INSERTING ONE SIDE PORTION OF A CORE BOARD ELEMENT OF OPEN-CELLED STRUCTURE INTO AND THROUGH SAID OUTER LAYER AND INTO ENGAGEMENT WITH SAID SUPPORT MEMBER, AND SAID SUPPORT MEMBER SEEPING SAID CORE BOARD ELENENT OUT OF CONTACT WITH SAID BASE, SO THAT SOME BINDER OF SAID OUTER LAYER ENTERS AND IS PICKED UP BY THE CELLS OF SAID CORE BOARD ELEMENT, AND FINALLY ALLOWING SAID BINDER TO HARDEN. 